title: Large-scale variation in combined impacts of canopy loss and disturbance on community structure and ecosystem functioning.
abstract: Ecosystems are under pressure from multiple human disturbances whose impact may vary depending on environmental context. We experimentally evaluated variation in the separate and combined effects of the loss of a key functional group (canopy algae) and physical disturbance on rocky shore ecosystems at nine locations across Europe. Multivariate community structure was initially affected (during the first three to six months) at six locations but after 18 months, effects were apparent at only three. Loss of canopy caused increases in cover of non-canopy algae in the three locations in southern Europe and decreases in some northern locations. Measures of ecosystem functioning (community respiration, gross primary productivity, net primary productivity) were affected by loss of canopy at five of the six locations for which data were available. Short-term effects on community respiration were widespread, but effects were rare after 18 months. Functional changes corresponded with changes in community structure and/or species richness at most locations and times sampled, but no single aspect of biodiversity was an effective predictor of longer-term functional changes. Most ecosystems studied were able to compensate in functional terms for impacts caused by indiscriminate physical disturbance. The only consistent effect of disturbance was to increase cover of non-canopy species. Loss of canopy algae temporarily reduced community resistance to disturbance at only two locations and at two locations actually increased resistance. Resistance to disturbance-induced changes in gross primary productivity was reduced by loss of canopy algae at four locations. Location-specific variation in the effects of the same stressors argues for flexible frameworks for the management of marine environments. These results also highlight the need to analyse how species loss and other stressors combine and interact in different environmental contexts.
authors.affiliation: School of Biology and Environmental Science, University College Dublin, Dublin, Ireland. tasman.crowe@ucd.ie
authors.forename: Tasman P
authors.initials: TP
authors.lastname: Crowe
authors.forename: Mathieu
authors.initials: M
authors.lastname: Cusson
authors.forename: Fabio
authors.initials: F
authors.lastname: Bulleri
authors.forename: Dominique
authors.initials: D
authors.lastname: Davoult
authors.forename: Francisco
authors.initials: F
authors.lastname: Arenas
authors.forename: Rebecca
authors.initials: R
authors.lastname: Aspden
authors.forename: Lisandro
authors.initials: L
authors.lastname: Benedetti-Cecchi
authors.forename: Stanislao
authors.initials: S
authors.lastname: Bevilacqua
authors.forename: Irvine
authors.initials: I
authors.lastname: Davidson
authors.forename: Emma
authors.initials: E
authors.lastname: Defew
authors.forename: Simonetta
authors.initials: S
authors.lastname: Fraschetti
authors.forename: Claire
authors.initials: C
authors.lastname: Golléty
authors.forename: John N
authors.initials: JN
authors.lastname: Griffin
authors.forename: Kristjan
authors.initials: K
authors.lastname: Herkül
authors.forename: Jonne
authors.initials: J
authors.lastname: Kotta
authors.forename: Aline
authors.initials: A
authors.lastname: Migné
authors.forename: Markus
authors.initials: M
authors.lastname: Molis
authors.forename: Sophie K
authors.initials: SK
authors.lastname: Nicol
authors.forename: Laure M-L J
authors.initials: LM
authors.lastname: Noël
authors.forename: Isabel Sousa
authors.initials: IS
authors.lastname: Pinto
authors.forename: Nelson
authors.initials: N
authors.lastname: Valdivia
authors.forename: Stefano
authors.initials: S
authors.lastname: Vaselli
authors.forename: Stuart R
authors.initials: SR
authors.lastname: Jenkins
mesh_terms: D000220:Adaptation, Biological; D059001:Aquatic Organisms / Q000502:physiology*; D044822:Biodiversity; D003247:Conservation of Natural Resources; D005060:Europe; D015999:Multivariate Analysis; D011157:Population Dynamics; D000461:Rhodophyta / Q000502:physiology*